The invention relates generally to mechanisms for controlling shifts in transfer cases and the like and more specifically to an integrated cam and fork assembly disposed upon a rotatable shift rail.
In both early and many modern transmissions and transfer cases, shifts between various speed ranges and operating conditions are often achieved by a manual linkage controlled by the vehicle operator. Frequently, such linkages include one or a plurality of parallel shift rails which may be translated out of a center, neutral position to a forward or rearward position to select a given gear or operating mode.
In contemporary consumer products such as sport utility vehicles and light and medium duty trucks, gear range and operating modes in transfer cases are now more commonly selected through the agency of an electromechanical, pneumatic or hydraulic operator. A variety of drive assemblies and intermediate linkages have been developed to achieve range selection and transfer case operating mode, e.g., lockup of a viscous clutch, a differential or modulating clutch to directly couple the primary and secondary drive lines.
These devices represent equally varying levels of complexity, sophistication, reliability and cost. Oftentimes, a sophisticated system which provides rapid and precise selection of gears or operating modes falls short from a reliability standpoint. Contrariwise, simple systems often do not provide positive, accurate or repeatable shifts although they are reliable.
The present invention is directed to a shift assembly which achieves both highly accurate positioning of a shift fork with a minimum of components and is thus highly reliable.